Sulfur Tetrahydride and Allied Superhydride Clusters: When Resonance Takes Precedence.

Sulfur offers a variety of bonding surprises compared to the parent oxygen atom of the chalcogen family. In the present work, we employ standard quantum chemistry methods to characterize formation of previously unrecognized sulfur tetrahydride (C4v -symmetric SH4 ) from hydrogen sulfide (H2 S) and molecular hydrogen (H2 ) on the ground state potential energy surface. The unusual intramolecular interactions of SH4 defy Lewis-like bonding conceptions, exhibiting the dominance of resonance-type donor-acceptor delocalizations well beyond those of SF4 (C2v sawhorse geometry) and other known tetrahalides. The distressed character of SH4 bonding also leads to exotic intermolecular structural motifs in clusters of pure (SH4 )n and mixed (SH4 ⋅⋅⋅H2 S)n composition. We evaluate structural, spectroscopic, and electronic properties for various 2D/3D coordination patterns and discuss how (SH4 ⋅⋅⋅H2 S)n -type building blocks may relate to recent experimental studies of superconductivity in high-pressure materials of "SH3 " stoichiometry.